SHORT-TERM EFFECTS OF AIR-POLLUTION ON EMERGENCY HOSPITAL ADMISSIONS FOR RESPIRATORY-DISEASE - RESULTS OF THE APHEA PROJECT IN 2 MAJOR CITIES IN THE NETHERLANDS, 1977-89

Study objective - To assess the short term relationship between air po llution and the daily number of emergency hospital admissions for resp iratory disease.Design - Data were analysed using autoregressive Poiss on regression allowing for overdispersion and controlling for possible confounding factors such as seasonal and other chronological variable s, meteorological factors, and influenza epidemics. Setting - The two major cities in The Netherlands - Amsterdam (694 700 inhabitants) and Rotterdam (576 200 inhabitants). Participants and measurements - Emerg ency hospital admissions for respiratory diseases, registered on a dai ly basis by the National Medical Registration, for the period 1977-89 were used. ICD-9 codes included were: respiratory (460-519), chronic o bstructive pulmonary disease (490-492, 494, 496), and asthma (493). Th e mean (range) of the total daily number of admissions for these three classifications were as follows: 6.70 (0-23), 1.74 (0-9) and 1.13 (0- 7) respectively in Amsterdam and 4.79 (0-19), 1.57 (0-9), and 0.53 (0- 5) in Rotterdam. Air pollution measurements were provided by the Natio nal Institute of Public Health and Environmental Protection. In The Ne therlands, air pollution is at a low to moderate (''summer type'') or a low (''winter type'') level. The levels in Amsterdam and Rotterdam d id not differ much for the ''summer type''. For 1977-89 the mean (rang e) values of ozone (O-3), the ''summer type'' pollutant (O-3-8 h), wer e 86 (0-252) mu g/m(3) in Amsterdam and 82 (0-286) mu g/m(3) in Rotter dam. The mean (range) of the values ''winter type'', pollutant, sulphu r dioxide (SO2-24 h), were 38 (0-381) mu g/m(3) in Amsterdam and 50 (1 -379) mu g/m(3) in Rotterdam. For black smoke (BS-24 h), values were 1 4 (1-84) mu g/m(3) and 28 (1-144) mu g/m(3) respectively (1986-89). Ma in results - Ozone had a non-significant positive effect on the number of respiratory emergency admissions in summer in people aged greater than or equal to 65 years (relative risk for a 100 mu g/m(3) increase in O-3-8 h of 1.127 (0.983, 1.292) in Amsterdam and a significant posi tive effect of 1.344 (1.097, 1.647) in 1977-81 in Rotterdam). Sulphur dioxide did not show any clear effects; in Amsterdam a significant neg ative effect was even found. The same was true for nitrogen dioxide in Amsterdam; in Rotterdam, however, nitrogen dioxide showed non-signifi cant positive effects (RR 0.965, 1.342). Black smoke did not show any clear effects in Amsterdam; in Rotterdam it was positively but not sig nificantly related to the number of admissions. Conclusions - The resu lts show that the relation between shortterm air pollution and emergen cy hospital admissions is not always consistent at these rather low le vels of daily hospital admissions and of air pollution.